It is hard to tell from the last picture, but it looks like the internal walls of the frames are vertical.
How far long are you with your build? What is your impression of these reeds?
The internal walls are vertial, yes.
the build is still in the head - It'll happen, but not for a long time I think, too many melodeon-based projects to try out first.
But the general impression with the reeds is good, especially considering the pricing. Not in the class of good hand-made concertina reeds, but like someone said earlier in this thread, they're likely somewhere between accordion (hybrid) reeds and true concertina reeds. I have only tried them on a tuning-table, and the results were promising, when the tongue was set correctly.